This invention relates in general to selective call units receiving messages, and particularly to optimizing memory utilization of a selective call unit in one-way messaging system that transmits fragmented messages.
Memory reservation is a standard procedure in two-way messaging systems. Before sending a message, the messaging system has the option of sending a query message to a selective call unit to establish that sufficient memory is available for storing a message. If the unit indicates that insufficient memory is available, the messaging system does not send the message. In some cases, the messaging system stores the message for future transmission on the theory that perhaps a few minutes later the selective call unit will have memory available to receive the message after, for example, the user of the unit having read messages and/or discarded messages from memory.
In contrast, sending a query to determine available memory capacity of a selective call unit is not possible in one-way messaging systems. Often one-way messaging systems using message fragmentation will transmit to a selective call unit a sequence of interspersed message fragments belonging to different messages, each message fragment including a portion of one of the messages transmitted, and information indicating the length of the message fragment. Because message fragments do not include information indicating the total length of the message being transmitted, a selective call unit receiving a sequence of interspersed message fragments will not know whether there is sufficient memory available to receive messages.
This leads to the situation where the selective call unit is unable to properly receive messages that could have otherwise been received individually, because memory is exhausted before all the message fragments for any one of the messages has been received. This may often result in the reception of one or more partially decoded messages, which generally is contrary to customer expectations.
Thus, what is needed is a method and apparatus that can improve utilization of memory in selective call units operating in one-way messaging systems that transmit fragmented messages.